Imagining a situation counter to the actual facts:

"This application leads us away from the notion of single causes that are necessary and sufficient. It leads us to ask instead whether the removal of one component of the constellation of circumstances would have prevented the outcome from occurring in this particular instance." (Susser E, Schwartz S, Morabia A, Bromet EJ. Psychiatric Epidemiology: Searching for the causes of mental disorders. Oxford University Press, 2006)